Vascular disease examining system and bypass vascular diagnosing device

ABSTRACT

Disclosed are a vascular disease examination system capable of examining and diagnosing vascular diseases such as arterial obliteration by determining the feature quantities of blood flow velocity waveforms or blood pressure waveforms or blood flow rates, and a bypass vascular diagnosing system. A blood flow velocity or blood pressure at a target location of the body is measured and the measurement signal is supplied to a vascular disease examination system  1 . The measurement signal is converted into a digital signal at an A/D conversion unit  2  and temporarily stored in a memory unit  3 . A waveform analysis unit  4  determines the feature quantity of a blood flow waveform (or blood pressure waveform), for displaying on an output unit  5 . The feature quantity includes a time constant, Fourier transform value, differentiated value, integrated value, rise/fall time, and sharpness or gradient of rise. Feature quantity of a blood flow velocity waveform (or blood pressure waveform) indicated in numeric value enables a correct examination/diagnosis.

TECHNICAL FIELD

[0001] The present invention relates to a vascular disease examinationsystem and a bypass vascular diagnosing system capable of examining anddiagnosing vascular diseases such as ischemic disease based on the bloodflow velocity waveforms, blood pressure waveforms or blood flow ratewaveforms.

DESCRIPTION OF RELATED ART

[0002] Conventional examination methods, which use a pressure sensorinvasively inserted into a blood vessel, or an ultrasonic Doppler flowsensor or a pressure sensor externally pressed against a blood vessel,have been well known. In case that a bypass surgery for supplying ablood flow into the downstream of a blood vessel by bypassing theoccluded portion using a graft (generically indicates implantedbiological blood vessels), the blood pressure, the blood flow velocity,and blood flow rate of given sites of a human body are measured andexamined to evaluate the effect of the bypass surgery.

[0003] For example, FIG. 19 is a view explaining the method forevaluating the prognosis of circulation reconstruction of a patient withlower leg ischemia by the bypass surgery. The lower leg ischemia iscaused by an occluded portion in anywhere in a downstream arterial lineto a lower leg, and the bypass surgery was performed on the patient tobypass the occluded portion for directing a blood flow into the lowerleg using a graft (generically indicates biological blood vessels). Thebypassed blood flow passes down through below knee artery 23 in thelower leg 21 to the top side 25 of a foot in FIG. 19. The prognosis ofcirculation reconstruction over the entire lower leg 21 can be evaluatedby pressing an ultrasonic Doppler velocity indicator 29 against the skinof the dorsal artery of foot 27 on the top side of foot 25.

[0004] In this case, the segmental blood pressure measurement method,which measures, examines, and compares the blood pressure, the bloodvelocity, and the blood flow rate of the given sites of a human body, isused and in particular, the Ankle/Brachial Pressure Index (API) methodand the Ankle/Brachial Blood Index (ABI, blood instead of pressure)method are well known. The API method measures both of blood pressuresat an upper arm and a lower leg, for example an ankle and the ratiobetween two blood pressures is assumed to be an API, based on which theseverity of a vascular disease is diagnosed. Similarly, in the case ofthe ABI method, the ratio between two blood flow rates is assumed to bean ABI. For example, a manchette is wound around the upper arm and thenthe ankle and pressurized followed by depressurization to measure theblood flow rates when the first beat is caught, based on which an ABIvalue is found. The blood flow rate on the top side of foot is found bypressing a velocity indicator 29 against the dorsal artery of foot 27 onthe top side of foot 25 to measure the blood velocity and assuming thevessel diameter. The blood flow rate on the upper arm can be found inthe same manner as that of the top side of foot.

[0005]FIG. 20 is a view explaining the method for evaluating theprognosis of circulation reconstruction through a graft implanted in apatient with a disease in the coronary artery, which supply nutrientsinto the heart, by the bypass surgery. The coronary artery braches fromthe ascending aorta 33 in the heart 31 into right coronary artery(generally, simply referred to as RCA) 35, left anterior descendingbranch (simply referred to as LAD) 37, the first and second diagonal(simply referred to as D), and left circumflex (simply referred to asCIRC) 41. In the figure, the left anterior descending branch 37 has beenbypassed using a graft 43. In this case, the sensor unit of the Dopplervelocity indicator 45 has been clipped on the circumference of the craft43 to evaluate the parameters such as the maximum value for the bloodflow rate of blood passing through the graft 43 during the surgery. Itshould be noted here that in the case of coronary-artery bypass surgery,the blood flow rate can be directly evaluated without assumption of thevessel diameter of the graft 43, by clipping the sensor unit around thecircumference of the graft 43, while since the opened chest is closedafter the surgery has been finished, the prognosis of circulationreconstruction can not be evaluated.

[0006] In addition, besides the above mentioned evaluation of ABI valuesand the maximum values for coronary-artery bypass vessel flow amounts,the measurement methods, in which for example arterial blood flowvelocity waveforms are represented in the form of frequency analysis orzero crossing, have been known.

[0007] Vascular diseases and bypass vessels can be evaluated andexamined using the segmental measurement method, in particular byevaluating ABI values of the patient with lower leg ischemia abovementioned and the maximum values for blood flow rates passing throughthe bypass vessel in a cardiac coronary artery. In the segmental bloodpressure measurement method for finding ABI values and others, it isnecessary to measure the blood flow rates at more than one given site.

[0008] In addition, during and immediately after the surgery, thepatient is in rest state and the blood flow velocity and the blood flowrate values of the patient are measured under the condition of theresting blood pressure. Ten days after the surgery, the prognosis ofcirculation reconstruction of the patient is evaluated under the bloodpressure condition in the normal daily life. Accordingly, in clinicalcases, for example the ABI value does not always keep pace with theprognosis of vessel reconstruction of the patient after the bypasssurgery. Similarly, the maximum value of blood flow rate of blood flowpassing through the coronary bypass vessel does not always keep pacewith the prognosis of vessel reconstruction.

[0009] In addition, expertise and experience are essential to diagnosediseases based on the displayed frequency analysis or zero crossing dataon arterial blood flow velocity waveforms.

[0010] The present invention is intended to solve these problems and theobject of the present invention is to provide a vascular diseaseexamination system and a bypass vascular examination system capable ofperforming an accurate and recognizable examination by finding thefeature quantities of the blood velocity waveform or the blood pressurewaveform or the blood flow rate and of comparing the results of theexamination with the prognosis of circulation reconstruction.

DISCLOSURE OF THE INVENTION

[0011] The vascular disease examining system of the present inventionintended to solve the problem above mentioned is characterized in thatit has a waveform analysis unit for obtaining the feature quantities ofthe waveform based on at least one of the blood flow velocity waveformsignals and the blood pressure waveform signals output from themeasurement system, which measures at least one of the blood flowvelocity and the blood pressure and an output unit for outputting thewaveform feature quantities found in the waveform analysis unit.

[0012] In addition, the bypass vascular diagnosing system of the presentinvention is characterized in that it has waveform analysis unit forobtaining the feature quantities of at least one of the blood flowvelocity waveform signals and the blood pressure waveform signals andthe blood flow rate waveform signals output from the measurement system,which measures one of the blood flow velocity and the blood pressure andthe blood flow rate and an output unit for outputting the waveformfeature quantities found in the waveform analysis unit. Moreover, withrespect to the vascular disease examination system or the bypassvascular diagnosing system, the waveform feature quantities arepreferably time constants.

[0013] Furthermore, with respect of the vascular disease examinationsystem or the bypass vascular diagnosing system of the presentinvention, the waveform feature quantities are preferably Fouriertransform values or differentiated values or integrated values.

[0014] Additionally, with respect to the vascular disease examinationsystem or the bypass vascular diagnosing system of the presentinvention, the waveform feature quantities are preferably therising/falling times of the waveform of at least one of the blood flowvelocity and the blood pressure and the blood flow rate.

[0015] Moreover, with respect to the vascular disease examination systemor the bypass vascular diagnosing system of the present invention, thewaveform feature quantities are preferably the sharpness of thewaveform.

[0016] Furthermore, with respect to the vascular disease examinationsystem or the bypass vascular diagnosing system of the presentinvention, the waveform feature quantities are preferably the slope of aline connecting two points, the lowest and highest values in one cycleof at least one of the blood velocity waveform and the blood pressurewaveform and the blood flow rate.

[0017] Furthermore, with respect to the vascular disease examinationsystem of the present invention, the waveform analysis unit preferablyfinds an equivalent resistance value and an equivalent compliance valuebased on at least one of the blood flow velocity waveform signal and theblood pressure waveform signal, respectively.

[0018] Additionally, with respect to the bypass vascular diagnosingsystem of the present invention, the waveform analysis unit preferablyfinds the equivalent resistance value and the equivalent compliancevalue of a bypass blood vessel based on at least one of the bloodpressure waveform signal and the blood flow rate waveform signal,respectively.

[0019] Moreover, the vascular disease examination system of the presentinvention is characterized in that it has an equivalent constantcalculation means for calculating the equivalent constant for the bloodvessel for establishing the relationship between the blood flow velocityand blood pressure based on the waveform signals output from ameasurement system, which measures the blood flow velocity and the bloodpressure and a dynamic bypass vascular condition calculation means forcalculating the blood flow velocity values under the virtual bloodpressure condition, in which a load is exerted on the blood vessel,using the equivalent constant to find the dynamic blood vesselcondition.

[0020] Furthermore, the bypass vascular examining system of the presentinvention is characterized in that it has an equivalent constantcalculation means for calculating the equivalent constant for the bypassblood vessel for establishing the relationship between the blood flowrate and blood pressure based on their waveform signals output from themeasurement system, which measures the blood flow rate and the bloodpressure and a dynamic bypass vascular condition calculation system forcalculating the blood flow rate under the virtual blood condition, inwhich a load is exerted on the bypass blood vessel to find the dynamicbypass vascular condition.

[0021] The vascular disease examination system of the present inventionextracts and outputs the feature quantities of the blood flow velocitywaveform of the blood pressure waveform when the measured signals of theblood flow velocity or the blood pressure are input. It enables aphysician to examine and diagnose vascular diseases based on the outputwaveform feature quantities.

[0022] By the analysis of an arterial blood flow velocity waveform, itis possible to evaluate the peripheral resistance and blood vesselcompliance, being useful in diagnosing nosovascular diseases.

[0023] The waveform feature quantity may be in the form of a timeconstant, a Fourier transform value, a differentiated value, integratedvalue, rising/falling times, or waveform sharpness.

[0024] Any difference in blood flow velocity waveform or blood pressurewaveform exists between a normal subject (control) and a patientsubject. For this reason, the vascular diseases can be examined anddiagnosed based on the waveform feature quantities.

[0025] Additionally, the waveform analysis unit is capable of performingmore definitive diagnoses based on the blood vessel resistance andcompliance values by finding them from the blood flow velocity waveformsignal and the blood pressure waveform signal, respectively.

[0026] This specification includes the content described in thespecification and drawings contained in JP-B No. 188032/2001 and JP-BNo. 262965/2001, on which the priority of the present application isbased.

BRIEF DESCRIPTION OF DRAWINGS

[0027]FIG. 1 is a view showing the block configuration of a vasculardisease examination system of the present invention.

[0028]FIG. 2 is a graph showing the blood flow velocity waveformmeasured on a patient with an arterial disease prior to the surgery.

[0029]FIG. 3 is a graph showing the blood flow velocity waveformmeasured on the patient immediately after the surgery.

[0030]FIG. 4 is a graph showing the blood flow velocity measured on thepatient one week after the surgery.

[0031]FIG. 5 is a view explaining one preferred embodiment of thepresent invention, in which a time constant is found as a waveformfeature quantity.

[0032]FIG. 6 is a view explaining another preferred embodiment of thepresent invention, in which sharpness is found as a waveform featurequantity.

[0033]FIG. 7 is a view showing the example of a blood flow rate waveformof a blood flow passing through the typical bypass blood vesselimplanted in cardiac coronary artery.

[0034]FIG. 8 is a view explaining further another preferred embodimentof the present invention, in which when the slope at waveform rising isused as a blood velocity waveform feature quantity, the slope isdefined.

[0035]FIGS. 9A and 9B are graphs showing the ABI values measured by theprior art system prior to, immediately after, and given days after thebypass surgery, and the result of the variation in normalized slope inone case obtained in the preferred embodiment of the present invention.

[0036]FIGS. 10A and 10B are graphs showing the ABI values measured priorto, immediately after, and given days after the bypass surgery, by theprior art system and the result of the variation in normalized slope inanother case obtained in the preferred embodiment of the presentinvention.

[0037]FIGS. 11A and 11B are graphs showing the ABI values measured priorto, immediately after, and given days after the bypass surgery, by theprior art system and the result of the variation in normalized slope infurther another case obtained in the preferred embodiment of the presentinvention.

[0038]FIG. 12 is a view explaining the preferred embodiment of thepresent invention, in which the normalized slope is defined for theblood flow rate of a cardiac coronary arterial bypass blood vessel.

[0039]FIGS. 13A and 13B are views showing the comparison between thesize of the normalized slope in the preferred embodiment of the presentinvention and the maximum value for blood flow rate in one case withthree bypass grafts implanted by the coronary arterial bypass surgery.

[0040]FIGS. 14A and 14B are views showing the comparison between thesize of the normalized slope in another preferred embodiment of thepresent invention and the maximum value for blood flow rate in one casewith three bypass grafts implanted by the coronary arterial bypasssurgery.

[0041]FIGS. 15A and 15B are views showing the comparison between thesize of the normalized slope in another preferred embodiment of thepresent invention and the maximum value for blood flow rate in one casewith three bypass grafts implanted by the coronary arterial bypasssurgery.

[0042]FIGS. 16A and 16B are views showing the comparison between thesize of the normalized slope in another preferred embodiment of thepresent invention and the maximum value for blood flow rate in one casewith three bypass grafts implanted by the coronary arterial bypasssurgery.

[0043]FIG. 17 is a view showing a model of electric circuit equivalentto the systemic circulation system.

[0044]FIG. 18 is a view showing a simple model of electric circuitequivalent to the systemic circulation system.

[0045]FIG. 19 is a view explaining the prior art method for evaluatingcirculation reconstruction on the patient with lower leg ischemia by thebypass surgery.

[0046]FIG. 20 is a view explaining the prior art method for evaluatingcirculation reconstruction of blood flow passing through a graftimplanted in the patient with a disease in coronary artery supplyingnutrients into the heart by the bypass surgery.

BEST MODE FOR CARRYING OUT THE INVENTION

[0047] Referencing to accompanying drawings, preferred embodiments ofthe present invention are described in detail.

[0048]FIG. 1 is the block configuration diagram of a vascular diseaseexamination system of the present invention. The vascular diseaseexamination system 1 has an A/D conversion unit 2, a memory unit 3, awaveform analysis unit 4, and an output unit 5. Symbol 10 indicates anultrasonic Doppler blood flow velocity measurement system (or bloodpressure measurement system). The blood flow velocity signals (or theblood pressure signals) of the target sites measured by the blood flowvelocity measurement system (or the blood pressure measurement system)10 are supplied into a vascular disease examination system 1.

[0049] The A/D conversion unit 2 converts the blood flow velocity (orblood pressure) waveform signals into digital waveform signals. Thedigital waveform signals are corresponded with time-series data andstored in a memory unit 3. A waveform analysis unit 4 finds waveformfeature quantities based on the digital waveform signals stored in thememory unit 3. This waveform analysis unit 4 is composed of a centralprocessing unit (CPU) or a digital signal processor (DSP) and a waveformanalysis program. An output unit 5 outputs the waveform featurequantities found at the waveform analysis unit 4. This output unit 5 iscomposed of an image display system, for example a monitoring device.Note that a printer for printing out the waveform feature quantityoutput from the output unit 5 may be incorporated in the output unit 5.

[0050] Almost similarly, in the block diagram of the bypass vascularexamining system according to another embodiment of the presentinvention, a blood flow rate measurement system (or blood pressuremeasurement system) may be used instead of the blood flow velocitymeasurement system 10 shown in FIG. 1, and the blood flow rate signals(or blood pressure signals) measured at the target sites are supplied tothe bypass vascular disease examination system instead of the vasculardisease examination system.

[0051] FIGS. 2 to 4 are views showing the results of the evaluation ofthe prognosis of circulation reconstruction by performing the bypasssurgery on the occluded artery of a patient with lower leg ischemia andpressing a Doppler blood flow velocity indicator against the dorsalartery of foot to obtain blood flow velocity signals. FIG. 2 is a graphshowing the blood flow velocity waveform measured on the patient witharterial disease prior to the surgery, FIG. 3 is a graph showing theblood flow velocity waveform measured on the patient immediately afterthe surgery, and FIG. 4 is a graph showing the blood flow velocitywaveform measured on the patient one week after the surgery. In thesegraphs, a vertical axis indicates blood flow velocity data and ahorizontal axis indicates time data. Note that the values along thehorizontal axis are indicated by corresponding sampling numbers used insampling blood flow velocity signals at a given sampling period.

[0052] As known from these graphs, in the case of a patient withadvanced arterial occlusion prior to the bypass surgery, therising-falling slope of the blood flow velocity waveform is moderate,while it is sharp after the surgery.

[0053]FIG. 5 is a view showing the example of a feature quantityextracted at the waveform analysis unit 5. In FIG. 5, a time constant isfound as a waveform feature quantity. The waveform analysis 4 recognizesone-peak rapid advanced phases based on, for example the normal valueson the normal side to cut out individual periods of a waveform relativeto their corresponding rapid advanced phases. The waveform analysis unit4 finds the time required for the blood flow velocity value to rise from0 up to about 63% of the peal value to be used as a rising timeconstant. The waveform analysis unit 4 finds the time required for theblood flow velocity value to drop from the peak value down to about 37%of the peak value to be used as a falling time constant. The waveformanalysis 4 finds the riding time and falling time constants for eachperiod, obtains an average for each of periods, and outputs the risingand falling time constants. Note that the waveform analysis 4 may findonly the rising time constant for outputting.

[0054] On the screen of the image display device, which is a componentof the output unit 5, not only the blood flow velocity waveform but alsothe rising and falling time constants are displayed. Based on thesedata, physicians and others can determine the severity of the vasculardisease. The time constant values obtained from the patients withvascular diseases such as angiostenosis and blood vessel occlusion tendto have large values.

[0055] Note that the thresholds for determining whether a patient isnormal and for determining the severity of the vascular disease musthave been established so that the waveform analysis unit 4 may comparethe calculated time constants with the associated thresholds fordetermining the severity of the vascular disease to output the resultsof the determination.

[0056] Alternatively, a Fourier transform value, a differentiated value,or an integrated value may be used as a waveform feature quantity.

[0057] Besides, sharpness may be used as a waveform feature quantity.FIG. 6 is a view showing the example of sharpness obtained as a waveformfeature quantity. The period up to the 50% point of the peak value forthe rapid advanced phase is found and the obtained value is assumed tobe a half-value width. The ratio of the period of the half-value widthto the period of one cycle (half-value width/cycle) is found and theobtained value is assumed t be sharpness.

[0058] Note that although in the preferred embodiments of the presentinvention, the feature quantity of the blood flow velocity waveform isobtained as an example, but the feature quantity of the blood pressurewaveform or the blood flow rate data may be obtained.

[0059] In FIG. 7 showing the example of the blood flow rate waveform ofblood flow passing through the typical cardiac coronary arterial bypass,the blood flow rate is measured by bypassing the occluded arterialportion into LAD using internal thoracic artery as a graft and clippingthe sensor unit of the Doppler blood flow rate indicator on the bypassblood vessel. The values along the horizontal axis indicate the timedata and the values along the vertical axis indicate blood flow ratedata. Note that the values along the horizontal axis are indicated bythe sampling number used in sampling.

[0060] The blood flow rate waveform of blood flow passing through thecardiac arterial bypass blood vessel shown in FIG. 7 has two peaks inthe rapid advanced phase within one heartbeat rhythm unlike those forthe dorsal artery of foot shown in FIGS. 2 to 4. This is caused by twoheart stroke periods, diastole, and systole. This means that blood issupplied into general peripheral artery in the diastole period, whileblood is easy to flow into cardiac coronary artery because the cardiacmuscle is relaxed even in the systole period, forming two peaks in therapid advanced phase corresponding to these periods.

[0061]FIG. 8 is a view showing the slope defined using the slope at awaveform starting point as a feature quantity of blood flow velocitywaveform obtained from the patient with lower leg ischemia. The lowestand highest points of the blood flow velocity are connected by a lineand the obtained slope is assumed to be a feature quantity. This sloperepresented by means of a blood flow velocity/time is converted into thevoltage/voltage waveform data at the blood flow velocity measurementsystem 10 and the waveform data is output directly to the output unit 5to be in the form of the length along the Y axis/length along the Xaxis. The normalization of these transformation gives the length alongthe Y axis and the length along the X axis of the graphic shown in FIG.8 for comparison.

[0062]FIGS. 9A and 9B and FIGS. 11A and 11B are graphs showing thevariation in normalized slope prior to, immediately after, and givendays after the bypass surgery. In this case, the obtained data wascompared with the ABI values.

[0063] For example, FIG. 9A shows variations in ABI value prior to,immediately after, and 17 days after the bypass surgery. Meanwhile, FIG.9B shows variations in normalized slope. In the case of this patient,the API value was slightly improved by the bypass surgery and 17 daysafter the surgery, the ABI value increased. The normalized slope wassignificantly improved by the bypass surgery, especially at the point of17 days after the surgery.

[0064] In the cases of the patients in FIGS. 10A and 10B, the ABI valuewas 0 prior to the bypass surgery and did not recovered even after thesurgery. On the other hand, the normalized slope was improved by thebypass surgery, and 11 days after surgery, the ABI value was recoveredand the normalized slope was significantly improved.

[0065] In the cases of the patients in FIGS. 11A and 11B, the ABI valuedropped down to 0 but the normalized slope was significantly recoveredby the bypass surgery and 10 days after the surgery, the ABI value wasslightly recovered but not to its original value prior to the surgery,while the normalized slope was more significantly improved.

[0066] Thus, examining variations in ABI value to evaluate whether thevalue is improved, not improved/decreased, and decreased, no variationsin ABI value keep pace with the prognosis of circulation reconstruction,while the normalized slope was outstandingly improved, keeping pace withthe prognosis of circulation reconstruction.

[0067] For this reason, it is understood that with respect to the bypasssurgery performed on the patient with lower leg ischemia, the normalizedslope of the blood flow velocity waveform of dorsal artery of foot isuseful for evaluating the prognosis of circulation reconstruction afterthe surgery, that is, it is an effective waveform feature quantity forthe blood vessel disease examining system.

[0068]FIG. 12 is a view explaining the defined normalized slope for theblood flow rate waveform of the cardiac coronary arterial bypass bloodvessel. In this case, since two types of waveforms were obtainedcorresponding to two periods of one heartbeat rhythm, distal andsystole, the slopes normalized to the rising time periods for the distaland systole periods were found and classified into S1 and S2. Similarly,the maximum values for the blood flow rate were classified into M1 andM2 corresponding to the distal and systole periods. In this case, theblood flow rate values were also normalized for comparison.

[0069]FIGS. 13A to 16B show the comparison in size between thenormalized slopes S1 and S2 and the maximum values M1 and M2 for bloodflow rate in the case with three bypass grafts implanted by the cardiaccoronary arterial bypass surgery. Three bypass points vary among theindividual patients, though three points are generally selected fromRCA, LCD, CIRC, and the first and second Ds.

[0070] For example, FIG. 13A shows the values for the normalized maximumblood flow rate at three bypass points rearranged in an ascending orderof values to find the rang of values. In this case, the minimum valuewas 0.15 and the maximum value was 0.45. FIG. 13B shows the normalizedcorresponding slopes rearranged in an ascending order of values to findthe range of values. The minimum value was 0.25 and the maximum valuewas 2.65.

[0071] Thus, no significant difference in maximum blood flow rate amongthree bypass blood vessels, namely focusing on the normalized blood flowrate only, no significant difference was observed in evaluating theprognosis of circulation reconstruction for the bypass blood vessel. Itis understood that a significant difference in normalized slope wasobserved in three bypass blood vessels.

[0072] Similarly, it may be applied to the different cases shown inFIGS. 14A, 14B, 15A, 15B, 16A, and 16B. Particularly, in the case ofcardiac coronary arterial bypass surgery, since the opened chest isclosed after the surgery has been finished, the evaluation of thecharacteristics of the bypass blood vessels provides a very useful meansin using the normalized slope as a feature quantity, which causes theevaluation of significant difference in circulation reconstruction.

[0073] Thus, it is understood that in the case of cardiac coronaryarterial bypass surgery, the normalized slope of the blood flow ratewaveform for the bypass blood vessel is effective feature quantity inevaluating the prognosis of circulation reconstruction by the bypasssurgery, namely for the bypass vascular examining system.

[0074]FIG. 17 is a view showing a model of electric circuit equivalentto the systemic circulation system. The characteristics of the bloodvessel include resistance R for the thinness of the blood vessel(equivalent to the resistance of an electric circuit) and compliance Cfor the softness of the blood vessel (equivalent to capacitance of theelectric circuit). The time constant can be obtained by multiplying C byR and is useful in diagnosing diseases, though resistance R andcompliance C are desirably obtained to achieve more definitivediagnosis. Namely, since the time constant discriminates between thethick and hard blood vessel and the thin and soft blood vessel, it isdesirable to handle independently two parameters R and C.

[0075] The model for the systemic circulation system can be representedas shown in FIG. 17 because a peripheral blood vessel has a largeresistance enabling the ignorance of compliance.

[0076] Where, Ra is arterial resistance, Ca is arterial compliance, Pais arterial blood pressure, Rp is peripheral blood vessel resistance, Rvis venous resistance, Cv is venous compliance, Pv is venous bloodpressure, and Ph is cardiac blood pressure.

[0077]FIG. 18 is a view showing the simple model of an electric circuitequivalent to the systemic circulation system. With respect to a vein,since its parameters are almost not changed due to physiological factorsand its arterial resistance Ra is smaller than its peripheral bloodvessel Rp and can be neglected, the model for the systemic circulationsystem may be more simplified.

[0078] To find resistance R and compliance C, one of these twoprocedures is followed.

[0079] (First method): The blood pressure (equivalent to voltage) andblood flow velocity (electric current) are measured and resistant R andcompliance C are identified, individually using any of methods such asthe least squares method. In the case of the use of the least squaresmethod, the model formula for the discrete system is established asshown below and using this formula 1 for the model, peripheral bloodvessel resistance Rp and arterial compliance Ca can be obtained frommany measured blood pressure values V (k) and blood flow velocity valuesI (k). $\begin{matrix}{{Formula}\quad (1)\text{:}} \\{{V\left( {k + 1} \right)} = {{\left( {1 - \frac{Ts}{CaRp}} \right)\quad {V(k)}} + {\frac{Ts}{Ca}\left( {1 - \frac{Ts}{2{CaRp}}} \right)\quad {I(k)}}}}\end{matrix}$

[0080] V(k): BP, HR CaRp: Time constant (slope)

[0081] Ts: Sampling time Ca: Compliance

[0082] I(k): Blood flow velocity or blood flow rate

[0083] (Second method): A shown in FIGS. 2A to 2B, since a relativelystable period(s) exists in a waveform cycle and in this period,compliance C may be ignored, resistance R is obtained by measuring theblood pressure and blood flow velocity values in this period, the timeconstants above mentioned are obtained, and compliance C can be foundfrom these time constants and resistance R.

[0084] For this reason, with respect to the first method, the formula 1,in which the model for the systemic circulation system shown in FIGS. 17and 18 is converted from the continuous system into the discrete(digital) system, is used to adapt them to computer-based calculations.Specifically, using many blood pressure values and blood flow velocityvalues measured in sampling as discrete data, the resistance andcompliance constants equivalent to the blood vessel, which are modelparameters, are obtained by the least squares method. With respect tothe second method, the resistance and compliance constants equivalent tothe blood vessel are obtained by measuring the blood pressure value inthe period in which the blood flow velocity is relatively stable aswell.

[0085] The equivalent constants obtained in this manner, which definethe relationship between the blood pressure and blood flow velocityvalues, are specific to the blood vessel, meaning that they stayunchanged under both of the resting and daily life conditions. Byobtaining the constants equivalent to the blood vessel using thisfeature, the relationship between the blood pressure and blood flowvelocity values measured on the patients under the various types ofdaily life styles.

[0086] The vascular disease examination system according to furtheranother embodiment of the present invention, which has the equivalentconstant calculation means for obtaining the equivalent constantsdefining the relationship between the blood pressure and blood flowvelocity values from the blood pressure and blood flow velocity valuesand the dynamic blood vessel condition calculation means for calculatingthe blood flow velocity value under the virtual blood pressurecondition, in which a load is exerted on the blood vessel using theobtained equivalent constants to obtain the dynamic blood vesselcondition value, is capable of predicting the dynamic condition of theblood vessel.

[0087] Namely, assuming that the blood vessel equivalent constants ofTs, Ca, and Rp are given in the formula 1, by substituting anappropriate blood pressure value V(k), the blood flow velocity i(k) canbe calculated under the condition of V(k). During and immediately afterthe bypass surgery, the patient lays rest in bed and the blood flowvelocity values measured under such conditions may differ from thosemeasured under the normal daily life condition given days after thesurgery. For this reason, the vascular disease examining system iscapable of calculating the blood vessel equivalent constants duringsurgery on a real time basis and estimating, based on the calculatedconstants, the blood flow velocity values under the condition of thenormal daily life given days after the surgery when the blood pressurevalues under the virtual normal daily life are substituted in theformula (1).

[0088] Similarly, the bypass vascular examining system according tofurther another embodiment of the present invention, which has theequivalent constant calculation means for obtaining the equivalentconstants defining the relationship between the blood pressure and bloodflow velocity values from the blood pressure and blood flow

1. A vascular disease examination system, comprising: a waveformanalysis unit for obtaining waveform feature quantities based on atleast one of the blood flow velocity and the blood pressure valuesoutput from a measurement system, which measures at least one of theblood flow velocity and the blood pressure values, and an output foroutputting the waveform feature quantities obtained at the waveformanalysis unit.
 2. A bypass vascular diagnosing system, comprising: awaveform analysis unit for obtaining waveform feature quantities basedon at least one of the blood flow velocity, the blood pressure, andblood flow rate values output from a measurement system, which measuresat least one of the blood flow velocity, the blood pressure, and bloodflow rate values, and an output for outputting the waveform featurequantities obtained at the waveform analysis unit.
 3. The vasculardisease examination system according to claim 1 or the bypass vasculardiagnosing system according to claim 2, wherein the waveform featurequantities are time constants.
 4. The vascular disease examinationsystem define in clam 1 and the bypass vascular diagnosing systemaccording to claim 2, wherein the waveform feature quantities areFourier transform values, differentiated values, or integrated values.5. The vascular disease examination system according to claim 1 or thebypass vascular diagnosing system according to claim 2, wherein thewaveform feature quantities are rising and falling times of at least oneof the blood flow velocity waveform and the blood pressure waveform andthe blood flow rate waveform.
 6. The vascular disease examination systemaccording to claim 1 or the bypass vascular diagnosing system accordingto claim 2, wherein the waveform feature quantity is the sharpness of awaveform.
 7. The vascular disease examination system according to claim1 or the bypass vascular diagnosing system according to claim 2, whereinthe waveform feature quantity is the slope of a line connecting theminimum and maximum values in one cycle of at least one of the bloodflow velocity waveform and the blood pressure waveform and the bloodflow rate waveform.
 8. The vascular disease examination system accordingto claim 1, wherein the waveform analysis unit finds resistance andcompliance equivalent to the blood vessel individually based on at leastone of the blood flow velocity and waveform signals.
 9. The bypassvascular diagnosing system according to claim 2, wherein the waveformanalysis unit finds resistance and compliance equivalent to the bloodvessel individually based on at least one of the blood flow velocity andwaveform signals.
 10. A vascular disease examination system, comprising:an equivalent constant calculation means for calculating the bloodvessel equivalent constants defining the relationship between the bloodflow velocity and the blood pressure based on the blood flow velocitywaveform signals and the blood pressure waveform signals output from ameasurement system, which measures the blood flow velocity and bloodpressure values, and a dynamic blood vessel condition calculation meansfor calculating the blood flow velocity values under the virtual bloodpressure condition, in which a load is exerted on the blood vessel usingthe equivalent constants to find the dynamic blood vessel condition. 11.A bypass vascular diagnosing system, comprising: an equivalent constantcalculation means for calculating the bypass blood vessel equivalentconstants defining the relationship between the blood flow velocity andthe blood pressure based on the blood flow velocity waveform signals andthe blood pressure waveform signals output from a measurement system,which measures the blood flow velocity and blood pressure values, and adynamic bypass vascular condition calculation means for calculating theblood flow velocity values under the virtual blood pressure condition,in which a load is exerted on the bypass blood vessel using theequivalent constants to find the dynamic bypass vascular condition.